Deposition of tungsten and tungsten-containing materials is an integral part of many semiconductor fabrication processes. Such deposition may be accomplished via chemical vapor deposition (CVD) techniques, plasma-enhanced CVD (PECVD) techniques, atomic layer deposition (ALD) techniques, as well as other deposition techniques known in the IC fabrication arts such as, for example, physical vapor deposition (PVD). Tungsten and tungsten-containing materials, hereinafter referred to as tungsten-based materials or just tungsten materials, may be used for horizontal interconnects, vias between adjacent metal layers, contacts between first metal layers and devices on the silicon substrate, and may generally be used within various high aspect ratio features utilized in IC design.
In a conventional process for depositing tungsten material, a substrate is heated to a predetermined process temperature in a deposition chamber, and a thin layer of tungsten material is deposited to serve as a seed or nucleation layer. Thereafter, a bulk layer of tungsten material is deposited atop the nucleation layer. Conventionally, the tungsten material is formed by the reduction of tungsten hexafluoride (WF6) with hydrogen (H2). Typically, tungsten material is deposited over an entire exposed surface area of the substrate which often includes one or more field regions, as well as various IC features. These features may have widely varying aspect ratios, and in some embodiments, one or more or all features may have relatively high aspect ratios.